"You're my sunshine" was the Namie Amuro（安室奈美恵）song that I liked the least out of all of the hits that were generated by the Okinawan dancer-singer during her first big boom from the mid-1990s. I'm not sure what it was but my impression was that it was a Jekyll-&-Hyde thing trying to fight over whether it was a pop song or a full-on dance tune. As I recall, it was one of the few Amuro songs that I couldn't remember in its entirety aside from the singer yelling either "I'm your sunshine!" or "You're my sunshine!" with a whole bunch of dance moves in between. Even trying to categorize it tonight, I couldn't decide whether this was R&B or techno or pop so I just went with the great equalizer and put down Pop.
Still, Amuro's 6th single from June 1996 was another one of her humongous hits, and the single and its commercials were all over the airwaves like butter on popcorn. Of course, Tetsuya Komuro（小室哲哉）was behind its creation. It was at No. 1 for two straight weeks (it was the 3rd-straight Amuro single to debut at the very top of the charts) and became the 13th-ranked song for the year, selling a total of over 1.3 million copies. "You're my sunshine" was also part of her first official album, "Sweet 19 Blues" which was released in July of that year and repeated the single's success by staying at No. 1 for two weeks. The album had even more success by attaining the No. 2 ranking for 1996 and becoming the 13th-ranked album in the history of Oricon, cracking through the 3-million sales ceiling.
One small piece of trivia that I gleaned from the article of the song on J-Wiki is that Tomomi Kahala（華原朋美）was part of the backup singing group.